On 2007-06-09 16:19:57 +0100, Roland Perry said:

In message , at 15:51:08 on Sat, 9 Jun 2007, Andy
Hall remarked:
- The piece of paper is too small to be read on a moving vehicle either
by eye or by camera
They are colour coded sufficiently that grossly out of date discs can
be easily spotted from a distance.
... and this happens how frequently?
I have no idea how often this visual clue is the trigger for a more
exhaustive investigation. But it's undeniable that the clue is more
obvious to an observer than the expiry date.

It remains pointless. The DVLA have records of cars and of when tax
was last paid. That is sufficient for the purposes of collecting tax.
It doesn't also need a piece of paper.

It does when enforcement continues to happen "on the streets".

That's an extremely inefficient way of doing enforcement in terms of ROI.